In recent years, various proposals have been made concerning UWB (Ultra Wide Band) radio communication methods. As UWB radio communication enables broadband communication exceeding 1 Gbps, its application to video transmission and the like with large transmission capacity has been investigated. On the other hand, UWB cannot be said to be easy to use in an office environment due to the narrowness of its possible communication range, and it can be said to be better suited to PANs (Personal Area Networks) that are attracting attention nowadays. However, PANs are still in their early days, and there are very few major applications. Since PANs have the broadband characteristics, a device utilizing PANs generally uses a lot of power, but in the case of a PAN, movement is difficult while carrying a large number of batteries.
One application that uses a PAN and requires the broadband characteristics of UWB is a file exchange (file-swapping, file-sharing) application. The basic operating principle of a file exchange application is disclosed in Patent Document 1, for example. It is possible to create a mini-community with random file exchange in a mobile environment (referred to as message exchange in Patent Document 1). Although not mentioned in Patent Document 1, exchanged data is not limited to text documents, and the exchange of music, image, video, and suchlike files is also possible. With UWB in particular, since the effective transmission speed is 100 Mbps to several Gbps, people can exchange large files that bypass each other, and this kind of file exchange can be said to be an application suited to UWB.
Various discussions concerning transmitting schemes used in this UWB have emerged in IEEE802.15. There are many cases in which a MAC protocol implemented in a PAN (and more particularly, a mobile PAN) environment is a scheme using autonomous distributed processing. This is because, in a PAN environment in which terminals constantly pass by each other, constructing a master-slave relationship each time, and starting communication after setting up a communication environment, such as assigning data slots, is a major overhead.
Further, the standardization of a radio communication apparatus in millimeter wave UWB is currently proceeded. In this regard, a plurality of radio communication schemes are proposed and argued. However, it is difficult to determine one scheme because these proposed schemes each have unique features. For example, ASK (Amplitude Shift Keying), PSK (Phase Shift Keying), and so on, are proposed for the modulation scheme. ASK can be implemented with a simple configuration, which can be manufactured extremely compact. On the other hand, PSK enables a faster transmission speed than ASK, yet involves a rather large apparatus configuration for ASK. To standardize these modulation schemes, a compartmentalization scheme in the same frequency band is required.
Non-Patent Document 1 discloses a radio communication scheme in an autonomous distribution type PAN.
FIG. 1 is a drawing showing the configuration of a super-frame in TDMA (Time Division Multiple Access).
In FIG. 1, a super-frame is divided into a beacon period 2201 and a data period 2202.
Beacons 2203 are transmitted from radio communication apparatuses within beacon period 2201, and it is guaranteed that beacons of neighboring nodes propagate to neighboring nodes without colliding.
Data period 2202 is divided equally per slot 2204, and slot IDs are assigned in that order, but this is not a limitation, and data periods may be unequal, and need not be contiguous.    Patent Document 1: Japanese Patent Application Laid-Open No. 2001-298406    Non-Patent Document 1: “Towards High Speed Wireless Personal Area Network-Efficiency Analysis of MBOA MAC”, Yunpeng Zang, et al.